The present invention relates to a melt-transfer device for the protected tapping of molten metal from one vessel to another, such as from a ladle to a pouring furnace.
When tapping molten metal from one vessel to another, it is difficult to prevent slag floating on the molten metal from accompanying the melt; at the same time there is a risk that the metal and any alloying materials it contains will become oxidized during the tapping operation since the stream of molten metal (referred to as the "tapping jet" hereafter) leaving the device is exposed to oxygen in the atmosphere. In addition, relatively high temperature losses can occur during the tapping operation because of the free radiation of thermal energy from the molten metal that can occur.
The above-noted considerations give rise to a problem when, for example, nodular iron containing magnesium has to be tapped into a pouring furnace. During the tapping,magnesium can be oxidized in the order of magnitude of 0.005-0.010%, while at the same time surface slag, largely consisting of FeO, SiO.sub.2 and MnO, is tapped into the furnace with the molten metal. This slag will adhere to the furnace lining or float up to the surface and is reduced by magnesium to form difficulty fusible slags which contain MgO. The formation of these modified slags results both in additional magnesium losses and in problems of the slag clogging passages in the furnace. Clogging can be a particular problem in the case of a channel-type pouring furnace.
One object of this invention is to provide a solution to the above-mentioned problems and other problems associated therewith.